本指南规范旨在为希望实施使用寿命设计原则和详细建议的机构提供设计建议。它的开发目的是将定量方法以及经证明符合规定的方法纳入一个单一的综合设计文件，以便在国家一级实施。它还为使用寿命设计建立了一个框架，同时提供了改进和扩展的机会，尤其是当能够模拟劣化机制的新模型可用时。 最近，人们对桥梁长期性能的期望发生了变化，人们将注意力集中在满足特定使用寿命的桥梁设计上。因此，除了AASHTO LRFD桥梁设计规范中已经包含的强度设计和适用性要求外，还呼吁扩大传统的极限状态，将重点放在耐久性上。在北美结构设计规范中，以耐久性为重点的极限状态没有明确确定，主要通过以下方式解决:- 满足需求。在过去的几十年中，已经进行了研究，以确定具体的耐久性极限状态，并制定合理的和定量的方法来考虑他们在设计阶段。本指南规范是NCHRP 12-108努力的成果，包括AASHTO、FHWA、NCHRP、战略公路研究计划2（SHRP2）以及其他国家和州资助的研究文件中包含的使用寿命指南。

This guide specification is intended to offer design recommendations for agencies wishing to implement service life design principles and detailing recommendations. It was developed to incorporate quantitative approaches, along with proven deemed-to-satisfy provisions, into a single comprehensive design document for implementation on a national level. It also establishes a framework for service life design, while providing opportunities for refinement and expansion, especially as new models capable of simulating deterioration mechanisms become available.Recent shifts in expectations regarding long-term performance of bridges have focused attention on the design of bridges to meet specific service lives. This has resulted in a call to expand traditional limit states to include a focus on durability in addition to the strength design and serviceability requirements already contained in the AASHTO LRFD Bridge Design Specifications. In North American structural design codes, durability-focused limit states are not explicitly identified and are addressed primarily through deemed-to-satisfy requirements. Over the last few decades, research has been conducted to identify specific durability limit states and to develop rational and quantitative approaches to consider them during the design phase. This guide specification is a product of the efforts of NCHRP 12-108 and includes the service life guidance contained in a number of AASHTO, FHWA, NCHRP, Strategic Highway Research Program 2 (SHRP2), and other national and state-sponsored research documents.